[PaleoMammalogy • 2024] Dianoconodon youngi • Fossils document Evolutionary Changes of jaw joint to mammalian middle ear

 

Dianoconodon youngi 

Mao, C. Zhang, Ren, T. Wang, G. Wang, F. Zhang, Rich, Vickers-Rich & Meng, 2024

DOI: doi.org/10.1038/s41586-024-07235-0  

 Researchgate.net/publication/379540254

Reconstruction by Chuang Zhao

Abstract

The dual jaw joint of Morganucodon consists of the dentary–squamosal joint laterally and the articular–quadrate one medially. The articular–quadrate joint and its associated post-dentary bones constitute the precursor of the mammalian middle ear. Fossils documenting the transition from such a precursor to the mammalian middle ear are poor, resulting in inconsistent interpretations of this hallmark apparatus in the earliest stage of mammaliaform evolution. Here we report mandibular middle ears from two Jurassic mammaliaforms: a new morganucodontan-like species and a pseudotribosphenic shuotheriid species. The morganucodontan-like species shows many previously unknown post-dentary bone morphologies and exhibits features that suggest a loss of load-bearing function in its articular–quadrate joint. The middle ear of the shuotheriid approaches the mammalian condition in that it has features that are suitable for an exclusively auditory function, although the post-dentary bones are still attached to the dentary. With size reduction of the jaw-joint bones, the quadrate shifts medially at different degrees in relation to the articular in the two mammaliaforms. These changes provide evidence of a gradual loss of load-bearing function in the articular–quadrate jaw joint—a prerequisite for the detachment of the post-dentary bones from the dentary and the eventual breakdown of the Meckel’s cartilage during the evolution of mammaliaforms.

Reconstruction of the newly described species Dianoconodon youngi.

illustration by Chuang Zhao 

Mammaliaformes Rowe, 1988

Dianoconodon youngi gen. et. sp. nov.

Holotype. A complete skull with associated dentitions and partialpostcranial skeleton (IVPP V4257, Institute of Vertebrate Paleontologyand Paleoanthropology, Chinese Academy of Sciences, Beijing) (Figs. 1and 2; Methods and Extended Data Figs. 1–6).

Etymology. Dian, the short form (Chinese phonetic Pinyin) of Yunnan Province, where the Lufeng fossil site is located; konos, Greek ‘cone’ or ‘cusp’; odon, Greek ‘tooth’. The specific name honours C. C. Young, who initiated the study of mammaliamorphs in Lufeng.  

Mandibular middle ears and transformation of the articular-quadrate joints in mammaliaforms. 

Fangyuan Mao, Chi Zhang, Jicheng Ren, Tao Wang, Guofu Wang, Fakui Zhang, Thomas Rich, Patricia Vickers-Rich and Jin Meng. 2024. Fossils document Evolutionary Changes of jaw joint to mammalian middle ear. Nature. DOI: doi.org/10.1038/s41586-024-07235-0 [03 April 2024]

 Researchgate.net/publication/379540254_Fossils_document_evolutionary_changes_of_jaw_joint_to_mammalian_middle_ear

 

[PaleoMammalogy • 2024] Feredocodon chowi • Jurassic shuotheriids show earliest dental diversification of mammaliaforms

 Feredocodon chowi

Mao, Li, Wang, Zhang, Rich, Vickers-Rich & Meng, 2024

 DOI: doi.org/10.1038/s41586-024-07235-0 

  Researchgate.net/publication/379540347

illustration by Chuang Zhao

Abstract

Shuotheriids are Jurassic mammaliaforms that possess pseudotribosphenic teeth in which a pseudotalonid is anterior to the trigonid in the lower molar, contrasting with the tribosphenic pattern of therian mammals (placentals, marsupials and kin) in which the talonid is posterior to the trigonid. The origin of the pseudotribosphenic teeth remains unclear, obscuring our perception of shuotheriid affinities and the early evolution of mammaliaforms. Here we report a new Jurassic shuotheriid represented by two skeletal specimens. Their complete pseudotribosphenic dentitions allow reidentification of dental structures using serial homology and the tooth occlusal relationship. Contrary to the conventional view, our findings show that dental structures of shuotheriids can be homologized to those of docodontans and partly support homologous statements for some dental structures between docodontans and other mammaliaforms. The phylogenetic analysis based on new evidence removes shuotheriids from the tribosphenic ausktribosphenids (including monotremes) and clusters them with docodontans to form a new clade, Docodontiformes, that is characterized by pseudotribosphenic features. In the phylogeny, docodontiforms and ‘holotherians’ (Kuehneotherium, monotremes and therians) evolve independently from a Morganucodon-like ancestor with triconodont molars by labio-lingual widening their posterior teeth for more efficient food processing. The pseudotribosphenic pattern passed a cusp semitriangulation stage, whereas the tribosphenic pattern and its precursor went through a stage of cusp triangulation. The two different processes resulted in complex tooth structures and occlusal patterns that elucidate the earliest diversification of mammaliaforms.

 Feredocodon chowi 

illustration by Chuang Zhao

Mammaliaformes Rowe, 1988

Shuotheridia Chow and Rich, 1982

 Feredocodon chowi

 

Fangyuan Mao, Zhiyu Li, Zhili Wang, Chi Zhang, Thomas Rich, Patricia Vickers-Rich and Jin Meng. 2024. Jurassic shuotheriids show earliest dental diversification of mammaliaforms. Nature. 628; 569–575. DOI: doi.org/10.1038/s41586-024-07235-0 [03 April 2024] 

  Researchgate.net/publication/379540347_Jurassic_shuotheriids_show_earliest_dental_diversification_of_mammaliaforms

 

[Paleontology • 2026] Isodapedon varzealis • A New hyperodapedontine rhynchosaur (Archosauromorpha: Rhynchosauria) from a Cynodont-dominated Site (Upper Triassic) of southern Brazil

 

Isodapedon varzealis  

Schiefelbein, Garcia, Doering & Müller, 2026

DOI: doi.org/10.1098/rsos.260176 

Artwork by Caio Fantini.

 

Abstract

We describe Isodapedon varzealis gen. et sp. nov., a new hyperodapedontine rhynchosaur from the Carnian deposits of the Candelária Sequence, southern Brazil. Phylogenetic analyses place this taxon outside known South American hyperodapedontines, including Macrocephalosaurus mariensis and ‘Hyperodapedon’ species, and support the restriction of the genus Hyperodapedon to its type species, thereby revealing greater diversity within the group than previously recognized. Isodapedon varzealis gen. et sp. nov. is characterized by symmetrical maxillary tooth bearing areas and distinctive dentary morphology, indicating divergent feeding adaptations relative to known rhynchosaurs. Stratigraphic occurrence in beds correlated with the Exaeretodon sub-zone of the Hyperodapedon Assemblage Zone, and its phylogenetic affinities with early diverging hyperodapedontines from Argentina and Scotland, imply a geographically widespread radiation of conservative morphotypes across southwestern Gondwana. This study highlights the complexity of Late Triassic rhynchosaur evolution and underscores the importance of continued palaeontological investigation in refining the taxonomy, biostratigraphy and palaeoecology of this key herbivorous clade.

Keywords: Rhynchosauria, Late Triassic, Candelária Sequence, Archosauromorpha

Subjects:palaeontology

Geological context of the Várzea do Agudo site and provenance of CAPPA/UFSM 0371. (A) Geologic map of the central region of Rio Grande do Sul (southern Brazil) showing the surface distribution of stratigraphic units of the Paraná Basin. (B) Field photograph of the Várzea do Agudo site. (C) Stratigraphic column of the Várzea do Agudo site depicting its fossiliferous content distribution. (D) Life reconstruction of CAPPA/UFSM 0371 by Caio Fantini. (E) Tridimensional model of the partial cranium of CAPPA/UFSM 0371 in right lateral view.

Abbreviations: cs, coarse-sandstone; Fm, formation; fs, fine-sandstone; g, gravel-sandstone; m, mudstone; ms, medium-sandstone. Silhouettes based on artwork by Caio Fantini and Felipe Elias.

Skull and lower jaws of Isodapedon varzealis gen. et sp. nov. (CAPPA/UFSM 0371).
(A) photographs, interpretative illustration and three-dimensional model from surface scan of the skull of CAPPA/UFSM 0371 in right lateral view. (B) Photographs, interpretative illustration and three-dimensional model from surface scan of the skull of CAPPA/UFSM 0371 in left lateral view.

Abbreviations: a, angular; aoc, anguli oris crest; d, dentary; jug, jugal; max, maxilla; mf, mental foramen; pmx l, left premaxilla; pmx r, right premaxilla; sa, surangular; sp, splenial. Black arrow points anteriorly.

Isodapedon varzealis gen. et sp. nov. craniomandibular elements.
 (A) Left skull in lateral view of Isodapedon varzealis gen. et sp. nov. (CAPPA/UFSM 0371) with emphasis on maxillary dentition area (occlusal view). (B) Left lower jaw in medial view with emphasis on lingual dentition area (oblique occlusal view).

Abbreviations: dg, diagonal gaps; lbt, labial teeth; lgt, lingual teeth; ls, longitudinal sulcus; sg, shallow groove; sms, short medial shelf. Black arrow points anteriorly.

Archosauromorpha 

Rhynchosauria  

Rhynchosauridae 

Hyperodapedontinae 

Isodapedon gen. nov.

Type and only species: Isodapedon varzealis sp. nov.

Etymology. The genus name is derived from the Ancient Greek ἴσος (ísos), meaning ‘equal’ or ‘the same’, as a reference to the equally wide tooth-bearing areas of the maxilla.

Isodapedon varzealis sp. nov.

Etymology. The species name refers to the locality of ‘Várzea do Agudo’ in which the specimen was collected.

Diagnosis. The holotype of Isodapedon varzealis is distinguished from all other known rhynchosaurids by the following unique combination of morphological traits (* asterisk denotes autapomorphies): maxilla divided into two tooth-bearing areas by a single longitudinal sulcus; equally wide maxillary lateral and medial tooth-bearing areas; same number (three) of longitudinal rows of teeth in both maxillary lateral and medial tooth-bearing areas; absence of lingual teeth in the medial surface of the maxilla; straight posterior margin of the parietal; sharp sagittal crest extending up to the posterior margin of the parietal; short and rounded ventral process of the squamosal; distinct posterior process in the squamosal; no contact between the lacrimal and palatine; ‘blunt’ and greatly reduced posteroventral process of the dentary; single dorsal blade in the dentary; medial shelf in the medial surface of the posterior portion of the dentary that does not reach half the length of the bone*; medial shelf separated from the dorsal blade of the dentary by a shallow groove; dorsal margin of the posterior portion of the dorsal blade extending markedly further dorsally than the posterior portion of the medial shelf at the level of the posteriormost lingual tooth; and single well-defined row of small, dorsally projected, closely packed lingual teeth in the dentary.

Artistic representation of a Late Triassic landscape of southern Brazil depicting individuals of Isodapedon varzealis gen. et sp. nov. in the foreground and a proterochampsid in the background.

Artwork by Caio Fantini.

 

Jeung Hee Schiefelbein; Maurício Silva Garcia; Mariana Doering and Rodrigo Temp Müller. 2026. A New hyperodapedontine rhynchosaur from a Cynodont-dominated Site (Upper Triassic) of southern Brazil. R Soc Open Sci. 13(4); 260176. DOI: doi.org/10.1098/rsos.260176 [15 Apr 2026]

[Paleontology • 2024] Riojanodon nenoi • A New early-diverging probainognathian cynodont and A Revision of the Occurrence of cf. Aleodon from the Chañares Formation, northwestern Argentina: New clues on the Faunistic Composition of the latest Middle–?earliest Late Triassic Tarjadia Assemblage Zone

Riojanodon nenoi

 Martinelli, Ezcurra, Fiorelli, Escobar, Hechenleitner, von Baczko, Taborda & Desojo, 2024

 DOI: 10.1002/ar.25388  

twitter.com/AnatRecord

 

Abstract

The Chañares Formation (Ischigualasto-Villa Unión Basin) is worldwide known by its exquisitely preserved fossil record of latest Middle-to-early Late Triassic tetrapods, including erpetosuchids, “rauisuchians,” proterochampsids, gracilisuchids, dinosauromorphs, pterosauromorphs, kannemeyeriiform dicynodonts, and traversodontid, chiniquodontid and probainognathid cynodonts, coming from the Tarjadia (bottom) and Massetognathus-Chanaresuchus (top) Assemblage Zones of its lower member. Regarding cynodonts, most of its profuse knowledge comes from the traditional layers discovered by Alfred Romer and his team in the 1960s that are now enclosed in the Massetognathus-Chanaresuchus Assemblage Zone (AZ). In this contribution we focus our study on the probainognathian cynodonts discovered in levels of the Tarjadia Assemblage Zone. We describe a new chiniquodontid cynodont with transversely broad postcanine teeth (Riojanodon nenoi gen. et sp. nov.) which is related to the genus Aleodon. In addition, the specimen CRILAR-Pv 567 previously referred to cf. Aleodon is here described, compared, and included in a phylogenetic analysis. It is considered as an indeterminate Aleodontinae nov., a clade here proposed to included chiniquodontids with transversely broad upper and lower postcanines, by having a cuspidated sectorial labial margin and a lingual platform that is twice broader than a lingual cingulum. Cromptodon mamiferoides, from the Cerro de Las Cabras Formation (Cuyo Basin), was also included in the phylogenetic analysis and recovered as an Aleodontinae. The new cynodont and the record of Aleodontinae indet. reinforce the faunal differentiation between the Tarjadia and Massetognathus-Chanaresuchus Assemblage Zones, in the lower member of the Chañares Formation, and inform on the diverse chiniquodontid clade with both sectorial and transversely broad postcanine teeth.

Keywords: Chiniquodontidae, Cynodontia, Probainognathia, South America, taxonomy

 

Riojanodon nenoi gen. et sp. nov.

 

Agustín G. Martinelli, Martín D. Ezcurra, Lucas E. Fiorelli, Juan Escobar, E. Martín Hechenleitner, M. Belén von Baczko, Jeremías R. A. Taborda and Julia B. Desojo. 2024. A New early-diverging probainognathian cynodont and A Revision of the Occurrence of cf. Aleodon from the Chañares Formation, northwestern Argentina: New clues on the Faunistic Composition of the latest Middle–?earliest Late Triassic Tarjadia Assemblage Zone. The Anatomical Record.  DOI: 10.1002/ar.25388

  twitter.com/AnatRecord/status/1752663017978814877

[Paleontology • 2024] Paratraversodon franciscaensis • Skull Anatomy and Paleoneurology of A New traversodontid (Therapsida: Cynodontia) from the Middle-Late Triassic of Brazil

 

 Paratraversodon franciscaensis

Kerber, Roese-Miron, Medina, da Roberto-da-Silva, Cabreira & Pretto, 2024

DOI: 10.1002/ar.25385

 

Abstract

Traversodontidae, a clade of gomphodont cynodonts, thrived during the Middle and Late Triassic, displaying a wide geographical distribution. During fieldwork in 2009, a new specimen was discovered in Ladinian/early Carnian stratigraphic layers in southern Brazil. Here, we describe this specimen and propose a new taxon closely related to Traversodon stahleckeri (Traversodontinae) but displaying a unique combination of traits (e.g., presence of a poorly developed suborbital process, mesiodistal length of the paracanine fossa similar to the length of the canine, short diastema between the fourth incisor and the upper canine, and coronoid process not entirely covering the distalmost lower postcanine). Furthermore, the endocranial anatomy of the new taxon was examined. The reconstruction of the cranial endocast revealed paleoneurological features consistent with non-Gomphodontosuchinae traversodontids. These features include the presence of a pineal body (but the absence of an open parietal foramen). These recent findings contribute significantly to our understanding of the evolutionary history and cranial anatomy of Middle-Late Triassic traversodontids, shedding light on the diversity and adaptations of non-mammaliaform cynodonts.

Keywords: Dinodontosaurus Assemblage Zone, Ladinian/Carnian, phylogeny, Traversodontidae

 Paratraversodon franciscaensis

Leonardo Kerber, Lívia Roese-Miron, Thais G. M. Medina, Lúcio da Roberto-da-Silva, Sérgio F. Cabreira and Flávio A. Pretto. 2024. Skull Anatomy and Paleoneurology of A New traversodontid from the Middle-Late Triassic of Brazil. The Anatomical Record. DOI: 10.1002/ar.25385

[Paleontology • 2023] Santagnathus mariensis • Old Fossil findings in the Upper Triassic Rocks of southern Brazil improve Diversity of traversodontid Cynodonts (Therapsida: Cynodontia)

 Santagnathus mariensis

Schmitt, Martinelli, Kaiuca, Schultz & Soares, 2023

DOI: 10.1002/ar.25244 

 twitter.com/mauriciosaurus 

Abstract

In this contribution we describe a new genus and species of gomphodontosuchine cynodont from the Late Triassic Hyperodapedon Assemblage Zone (AZ) of the Santa Maria Supersequence of southern Brazil, based on material collected 20 years ago. The new taxon, Santagnathus mariensis gen. et sp. nov., is based on numerous cranial and postcranial remains, which altogether provide data on several parts of the skeleton. Santagnathus mariensis is closely related to Siriusgnathus niemeyerorum and Exaeretodon spp. and expands the knowledge about gomphodontosuchine cynodonts. Morphologically, the new species has a skull bauplan particularly similar to S. niemeyerorum and E. riograndensis, differing from them by a unique combination of traits such as three upper incisors, the absence of a descending process in the jugal, a more posterior position of the postorbital bar and a preorbital region larger than the temporal one. The new traversodontid was found associated with the rhynchosaur Hyperodapedon sp., corroborating the assignment of the cynodont fossils to the Hyperodapedon AZ. We also provide comments on the status of the Argentine traversodontid cynodont Proexaeretodon vincei, typically considered a junior synonym of Exaeretodon argentinus, and here accepted as a valid taxon.

Keywords: Eucynodontia, Late Triassic, Santa Maria Supersequence, Traversodontidae

 Santagnathus mariensis gen. et sp. nov.

 

Maurício Rodrigo Schmitt, Agustín Guillermo Martinelli, João Felipe Leal Kaiuca, Cesar Leandro Schultz, Marina Bento Soares. 2023. Old Fossil findings in the Upper Triassic Rocks of southern Brazil improve Diversity of traversodontid Cynodonts (Therapsida, Cynodontia). The Anatomical Record. 

DOI: 10.1002/ar.25244

  twitter.com/mauriciosaurus/status/1663194122847412227

[Paleontology • 2020] Agudotherium gassenae • A New Prozostrodontian Cynodont (Eucynodontia, Probainognathia) from the Upper Triassic of Southern Brazil

Agudotherium gassenae   

Stefanello, Kerber, Martinelli & Dias-Da-Silva, 2020

 DOI: 10.1080/02724634.2020.1782415   

 twitter.com/KerberLeonardo 

 

ABSTRACT

Probainognathian cynodonts are well represented in the fossil record from the Middle and Upper Triassic of South America, especially in Brazil and Argentina. In this contribution, we describe a new genus and species of non-mammaliaform prozostrodontian cynodont from southern Brazil. The new taxon comes from the Niemeyer Site, a locality in which the traversodontid cynodont Siriusgnathus niemeyerorum is numerically dominant, whereas probainognathians and other tetrapods are comparatively scarce. The fauna from the Niemeyer Site was putatively assigned to the Riograndia Assemblage Zone (Norian age) recently, although none of the index fossils for that biozone (e.g., Riograndia, Clevosaurus, Jachaleria) have so far been discovered at this locality. The new cynodont taxon is based on a left lower jaw with the canine and six (pc2–pc7) well-preserved postcanines (CAPPA/UFSM 0262, holotype), and a second referred specimen (CAPPA/UFSM 0208, paratype), which includes a right lower jaw with incisors, canine, and seven (pc1–pc7) postcanines, with pc6–pc7 being the best preserved. These specimens have a robust dentary, a long and dorsoventrally tall Meckelian groove, unserrated canines, and unserrated, sectorial postcanine teeth with posteriorly inclined cusps and a poorly developed lingual cingulum. This combination of features is unknown in other Carnian and Norian non-mammaliaform cynodonts. The new taxon contributes to our knowledge of the evolutionary radiation of small prozostrodonts that occurred in western Gondwana during the Late Triassic and led to the emergence of several important cynodont groups, including Mammaliaformes.

SYSTEMATIC PALEONTOLOGY 

THERAPSIDA Broom, 1905 

CYNODONTIA Owen, 1861 

EUCYNODONTIA Kemp, 1982 

PROBAINOGNATHIA Hopson, 1990 

PROZOSTRODONTIA Liu and Olsen, 2010 

Agudotherium gassenae, gen. et sp. nov.

Etymology—‘Agudo,’ in reference to the municipality of Agudo (state of Rio Grande do Sul, Brazil) where the specimens were found. The suffix ‘therium’ (from the Greek ‘thērion’) means ‘beast,’ and is often used for mammals and closely related forms. The specific epithet honors Mrs. Valserina Maria Bulegon Gassen, former mayor of the city of São João do Polesine (State of Rio Grande do Sul, Brazil), for her valuable contribution in the creation of CAPPA/UFSM.

Micheli Stefanello, Leonardo Kerber, Agustin G. Martinelli and Sérgio Dias-Da-Silva. 2020. A New Prozostrodontian Cynodont (Eucynodontia, Probainognathia) from the Upper Triassic of Southern Brazil. Journal of Vertebrate Paleontology. 40(3): e1782415. DOI: 10.1080/02724634.2020.1782415  

  twitter.com/KerberLeonardo/status/1314546070689636361

[Paleontology • 2019] Vetusodon elikhulu • A New Large Cynodont from the Late Permian (Lopingian) of the South African Karoo Basin and its Phylogenetic Significance

Vetusodon elikhulu

Abdala, Gaetano, Smith & Rubidge, 2019

DOI: 10.1093/zoolinnean/zlz004 
Artwork by Gabriel Lio.  twitter.com/GabrielLuisLio

Abstract

The Karoo Basin of South Africa has the best global record of Lopingian (Late Permian) non-mammaliaform cynodonts, currently represented by five species. We describe Vetusodon elikhulu gen. et sp. nov., documented by four specimens from the Daptocephalus Assemblage Zone. With a basal skull length of ~18 cm, it is the largest Lopingian cynodont and is also larger than Induan representatives of the group. Vetusodon elikhulu has a cranial morphology that departs notably from that previously documented for Permo-Triassic cynodonts. It features a short and extremely wide snout, resembling that of the contemporaneous therocephalian Moschorhinus, and has large incisors and canines that contrast with the small unicusped postcanines, suggesting a more important role of the anterior dentition for feeding. The dentary is extremely long and robust, with the posterior margin located closer to the craniomandibular joint than in other Lopingian and Induan cynodonts (e.g. Thrinaxodon). The secondary palate morphology of V. elikhulu is unique, being short and incomplete and with the posterior portion of the maxilla partly covering the vomer. A phylogenetic analysis suggests that V. elikhulu is the sister taxon of Eucynodontia and thus the most derived of the Lopingian to Induan cynodonts yet discovered.

Keywords: anatomy, Changhsingian, epicynodont, Gondwana, phylogeny

Life reconstructions of Vetusodon elikhulu. 

Artwork by Gabriel Lio.  

twitter.com/GabrielLuisLio

Life reconstructions of Vetusodon elikhulu.

 Artwork by Gabriel Lio. 

Vetusodon elikhulu gen. et sp. nov.

Fernando Abdala, Leandro C. Gaetano, Roger M. H. Smith and Bruce S Rubidge. 2019. A New Large Cynodont from the Late Permian (Lopingian) of the South African Karoo Basin and its Phylogenetic Significance. Zoological Journal of the Linnean Society. zlz004. DOI: 10.1093/zoolinnean/zlz004

 twitter.com/GabrielLuisLio/status/1137058332185956352

twitter.com/CONICETDialoga/status/1137068927761170440

Vetusodon elikhulu: when the old has something modern conicet.gov.ar/vetusodon-elikhulu-when-the-old-has-something-modern

[Paleontology • 2019] Ufudocyclops mukanelai • A New Kannemeyeriiform Dicynodont from Subzone C of the Cynognathus Assemblage Zone, Triassic of South Africa, with Implications for Biostratigraphic Correlation with other African Triassic Faunas

Ufudocyclops mukanelai

Kammerer, Viglietti, Hancox, Butler & Choiniere, 2019

 DOI: 10.1080/02724634.2019.1596921 

 twitter.com/Synapsida

ABSTRACT

A new taxon of kannemeyeriiform dicynodont, Ufudocyclops mukanelai, is described based on a well-preserved skull from Subzone C of the Cynognathus Assemblage Zone, which are the youngest strata (probably Middle Triassic) of the Beaufort Group (uppermost Burgersdorp Formation) in South Africa. Ufudocyclops mukanelai is diagnosed by its autapomorphic intertemporal morphology: the intertemporal bar in this taxon is ‘X’-shaped—broad anteriorly and posteriorly but distinctly ‘pinched’ at mid-length and bears a deep, triangular depression immediately behind the enormous pineal foramen. The new kannemeyeriiform can also be diagnosed by the presence of a laterally expanded jugal plate beneath the orbit, and highly discrete, ovoid nasal bosses separated by a broad, unornamented median portion of the premaxilla and the nasals. Two partial dicynodont skulls from this subzone, previously identified as specimens of the otherwise Tanzanian taxon Angonisaurus, are also referable to U. mukanelai. Removal of these specimens from the hypodigm of Angonisaurus eliminates a crucial point of correlation between Cynognathus Subzone C and the Manda Beds of Tanzania and suggests that Subzone C preserves a distinct, endemic fauna, not just a southern extension of the better-known Middle–Late Triassic tetrapod faunas from Tanzania and Zambia. Inclusion of Ufudocyclops in a phylogenetic analysis of anomodonts recovers it as an early stahleckeriid, the first record of this clade from the Cynognathus Assemblage Zone.

FIGURE 4. Ufudocyclops mukanelai, gen. et sp. nov., BP/1/8208, holotype, photograph and interpretive drawing in right lateral view. Gray indicates matrix; dotted lines indicate missing bone.

 Abbreviations: af, fossa for M. adductor mandibulae externus lateralis; cp, caniniform process of maxilla; fo, fenestra ovalis; fr, frontal; j, jugal; la, lacrimal; mx, maxilla; na, nasal; pa, parietal; pmx, premaxilla; po, postorbital; pr?, prootic; prf, prefrontal; pt, pterygoid; q, quadrate; smx, septomaxilla; sq, squamosal. Scale bar equals 5 cm.

FIGURE 10. Ufudocyclops and Angonisaurus compared.
A, B, holotype of Ufudocyclops mukanelai (BP/1/8208) in A, dorsal and B, right lateral views.
C, D, holotype of Angonisaurus cruickshanki (NHMUK PV R9732) in C, dorsal and D, left lateral views; D is mirrored for comparative purposes. Scale bars equal 5 cm.

SYSTEMATIC PALEONTOLOGY

 SYNAPSIDA Osborn, 1903 

THERAPSIDA Broom, 1905 

ANOMODONTIA Owen, 1860 

DICYNODONTIA Owen, 1860 

KANNEMEYERIIFORMES Maisch, 2001 

STAHLECKERIIDAE Lehman, 1961 

UFUDOCYCLOPS MUKANELAI, gen. et sp. nov.

Etymology— From the Xhosa ufudo, meaning tortoise (in reference to the toothless, tortoise-like beak), and the Ancient Greek cyclops, a one-eyed mythological giant (in reference to the enormous opening for the pineal eye on the dorsal midline of the skull). Species named in honor of Mr. Pepson Mukanela, in recognition of his many years working in the preparatory laboratory of the Evolutionary Studies Institute (and its predecessor, the Bernard Price Institute for Palaeontological Research) and in particular his skillful preparation of BP/1/8208.

Christian F. Kammerer, Pia A. Viglietti, P. John Hancox, Richard J. Butler and Jonah N. Choiniere. 2019. A New Kannemeyeriiform Dicynodont (Ufudocyclops mukanelai, gen. et sp. nov.) from Subzone C of the Cynognathus Assemblage Zone, Triassic of South Africa, with Implications for Biostratigraphic Correlation with other African Triassic Faunas. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2019.1596921 

 twitter.com/Synapsida/status/1130828704039329792

[Paleontology • 2019] The Postcranial Anatomy of Brasilodon quadrangularis and the Acquisition of Mammaliaform Traits Among Non-mammaliaform Cynodonts

Brasilodon quadrangularis 

Bonaparte, Martinelli, Schultz & Rubert, 2003

 from the Riograndia Assemblage Zone of the Candelária Sequence, Santa Maria Supersequence (Brazil).

  Illustration: Jorge Blanco. 

in Guignard, Martinelli & Soares, 2019. 

 DOI: 10.1371/journal.pone.0216672

Abstract

Brasilodon quadrangularis (Cynodontia, Probainognathia) is an iconic non-mammaliaform cynodont from the Late Triassic of Brazil (Riograndia Assemblage Zone, Candelária Sequence), being considered as the sister taxon of Mammaliaformes. Although its phylogenetic position is very important, several aspects of its postcranial anatomy remain unclear or unstudied. Here, we present a detailed description of the postcranial elements referred to Brasilodon, including previously mentioned specimens and new ones, which add relevant information about its postcranial morphology and provide a new insight into the anatomical transition between advanced non-mammaliaform cynodonts and early mammaliaforms. Functional and ecological implications are also investigated, based on the postcranial morphology and muscular reconstructions. The postcranium of Brasilodon differs from most non-mammaliaform cynodonts and presents similarities with tritylodontids, early mammaliaforms and extant therians, such as a ventrally oriented scapular glenoid facet, a distinct and ossified greater humeral tubercle, lack of ectepicondylar foramen, olecranon process, hemispherical humeral and femoral heads and a prominent intertrochanteric crest. The humeral torsion, the length of the deltopectoral crest, the large bicipital groove and the well-developed lesser tubercle, indicate that the forelimb of Brasilodon was hold in a semi-sprawling position, with well-developed adductor muscles to maintain the body off the ground. The short femoral neck and the strong medial projection of the femoral head indicate the femur was held in a more erect posture than in basal non-mammaliaform cynodonts. The anterodorsally projected iliac blade with reduced postacetabular process, reduction of the anterior part of the pubis, medially located lesser trochanter indicate a basically mammalian pattern of pelvic musculature, able to swing the femur in a nearly parasagittal plane.

Fig 13. Paleoartistic reconstruction of Brasilodon quadrangularis (left) and Riograndia guaibensis (right), two abundant probainognathian cynodonts from the Riograndia Assemblage Zone of the Candelária Sequence, Santa Maria Supersequence (Brazil), which exhibits different morphologies in skull, dentition and locomotor apparatus.

 Illustration: Jorge Blanco.

Conclusion: 

The postcranium of Brasilodon quadrangularis differs from other non-mammaliaform cynodonts and is similar to early mammaliaforms and extant therians (e.g., hemispherical humeral and femoral head, distinct greater tubercle of the humerus, circular acetabulum, salient intertrochanteric crest of the femur). The morphology of the ulnar condyle of the humerus and olecranon process of the ulna suggests more abilities for extension and flexion of the elbow, a necessary component for a parasagittal locomotion. However, the humeral torsion, the length of the deltopectoral crest, the large bicipital groove and the well-developed lesser tubercle, indicate that the forelimb of B. quadrangularis was hold in a semi-sprawling position, with well-developed adductor muscles to maintain the body off the ground. The short femoral neck and the strong medial projection of the femoral head indicate the femur was held in a more erect posture than in basal non-mammaliaform cynodonts. The anterodorsally projected iliac blade with reduced postacetabular process, enlarged obturator foramen, reduction of the anterior part of the pubis, prominent and distinctive greater trochanter, medially located lesser trochanter, narrow intertrochanteric fossa represent a further continuation of trends that indicates a basically mammalian pattern of pelvic musculature, able to swing the femur in a nearly parasagittal plane.

Although fossorial or semifossorial habits appear to have been common in derived non-mammaliaform probainognathians (i.e., Riograndia, Irajatherium and Kayentatherium), the postcranial study of B. quadrangularis shows more generalized adaptations and highlights that distinctive ecological strategies (Fig 13) were developed among small-sized non-mammaliaform cynodonts.

 Morgan L. Guignard, Agustin G. Martinelli and Marina B. Soares. 2019. The Postcranial Anatomy of Brasilodon quadrangularis and the Acquisition of Mammaliaform Traits Among Non-mammaliaform Cynodonts.  PLoS ONE. 14(5): e0216672. DOI: 10.1371/journal.pone.0216672